I did a lot of work with my headlights when I was doing my projector retrofit on my 2000 Tahoe, and at least on OEM headlamp assemblies, this is not completely accurate.
On OEM assemblies both the up/down and left/right adjusters are torx screws. The metal they are made of is soft and they strip out easily, so I found that a better way to adjust is to use a socket that fits over the adjustment screw. I cannot remember the size, but the adjustment screws are shaped so that you can adjust them with the torx screw or a socket that fits on the outside. I found the socket made it easier to make large adjustments and then used the torx to fine tune the settings.
The left/right adjustment is the screw towards the center plane of the truck, and the up/down adjustment is the screw closer to the fender.
Be careful when making adjustments on OEM assemblies, the metal is soft and the adjusters are brittle, so they are easily damaged. I recommend removing a headlamp just to get a better visual of how the assembly works before putting them back in and making the adjustments.